We've cruised on the Magic 12 times, and done WDW both before and after. In my opinion, parks before are better. We really wear ourselves out in the parks, so the cruise is relaxing for the mom, easy on the feet, etc.
Ditto the part about the food is free on the ship--the kids get used to the idea of getting ice cream whenever or if they don't like something, just getting something else.
We always have a little adjustment issue after the cruise (I've been known to say "Do I look like (name of server or steward)? Then get up and get it yourself!" They do get a little spoiled. I'd rather deal with that issue at home than in the parks.